The most famous loop of all times, "Amen Break", is a six second drum sample that starts at 1:26 on The Winstons song, Amen Brother. This sample was used extensively in early hiphop and sample based music, and became the basis for drum and bass and jungle music. A six second clip that spawned several subcultures has been used by many of the world's top DJs and Producers.
Watch this video about the Amen Break:
The Wikipedia source for The Winstons:
"The Winstons were a 1960's funk and soul music group, based in Washington, D.C.. They are known for their 1969 recording of an EP featuring a song entitled "Color Him Father" on the A-side, and a song entitled "Amen, Brother" on the B-side. Half-way into "Amen, Brother", there is a drum solo, performed by G.C. Coleman, which would cause The Winston's EP to become one of the most widely-sampled records in the history of electronic music. Sampled audio clips of the drum solo became known as the Amen Break, which has been used in thousands of tracks in a large number of musical genres, including drum and bass, hip hop, jungle, big beat, industrial, and electronica.
The "Color Him Father" record sold over one million copies, and received a gold record awarded by the Recording Industry Association of America on 24 July 1969."